Often planets are seen as circular or half-circular shapes, free-floating in space. Sometimes they are covered with pink goo, point boxes or hazardous material, such as spikes. The material they are covered in varies from level to level.
Depending on the level, Rockitty will either lose health, stick to planets or bounce off them. In most cases, they are used as a means of transportation to get to other not easily reachable areas in a level.